For quantitative magnetic image analysis it is important that the value of the magnetic field applied to the sample is known. Calibration of the magnetic field inside an electron microscope is not a simple procedure, however, because it requires the use of a special sample holder which contains a Hall probe sensor. We report here on a simple and effective procedure for calibration of the magnetic field at the sample position of the JEOL 3000 FEG transmission electron microscope (equipped with ultra-high resolution pole pieces URP-32F, point resolution of 1.6 Å and tilt angle ±30°) without the use of a special sample holder. The technique is based upon the fact that the magnetic flux present in a magnetized material in a field-free environment, known as the remanence Br, is a sensitive function of the largest applied magnetic field. The inverse of this principle — that the value of an applied field may be determined from measurements of the remanence, — was used to quantify the magnitude of the field present at the sample position.